For many decades, paper companies have wrapped their product rolls (such as paper rolls and other packages) in heavy kraft paper or other flexible and durable materials to protect them from damage in transit or storage. The process of wrapping the package generally consists of placing a covering of this material (called “roll wrap” which is derived from a “wrapper stock”) around the circumference of the paper roll (also called a “bilge”), attaching an inner protective disc (“inner head”) of heavy paper, chip board or corrugated medium against each paper roll end, crimping the excess roll wrap against the ends of the paper roll or inner head, and gluing/sealing an outer protective disc of heavy paper (“outer head”) on to the crimped roll wrap and/or the inner head.
The roll wrap is typically selected from the available widths of wrapper stock in unwind stands (“backstands”) used in the wrapping facility, and is usually substantially wider than the paper roll. The extra width, called the wrap overhang, is distributed more or less equally at each end of the paper roll, and ultimately forms the crimped portion of the package. In small manual wrapper systems, crimping is usually done by hand. In automated wrapping systems, individual paper rolls are typically transferred to wrapping platforms on which they are wrapped by roll wrap.
Wrapper stock is stored in the form of rolls of varying widths in the wrapping system. Each individual width is in its own backstand. In automated wrapping systems, the diameter and width of each incoming paper roll is measured by a control system. This system selects the best wrapper stock width from the available choices and calculates what length of wrapper must be provided to the given paper roll diameter to give the number of wrapper convolutions of wrapper required by the client. Depending on the needs of the client and the availability of particular widths of wrapper stock, the wrapper may or may not be optimal for the width of the roll.
In automatic wrapping systems, the wrapper stock is fed close to the paper roll, and glue is applied to the leading edge. The wrapper stock is advanced until it is pinched between the paper roll and a set of turning platform rollers on which the paper roll is resting. The platform rollers are actuated at the same speed as the wrapper stock supply speed and the wrapper stock is pinched between the paper roll and the turning rollers. The wrapper stock adheres to the paper roll and is carried around the paper roll until the correct number of convolutions has been applied. The system is stopped, the wrapper stock is severed and, simultaneously, a strip of glue is applied to the tail end of the roll wrap derived from the wrapper stock.
The platform rollers are restarted, drawing the tail end into a pinch point causing the tail of the roll wrap to adhere to the convolutions already applied. At this point, the roll wrap overhangs the paper roll ends forming a large “tube”. The length of the overhang depends on the width of the wrapper stock used and the length of the paper roll to be wrapped. After inner heads are inserted and retained at the ends of the paper roll, the wrap overhang is crimped.
As is understood in the art, crimping of the wrap overhang typically involves folding down the ends of the roll wrap towards the end of the paper roll. Crimping can also include creasing the folded wrap overhang to maintain the folds on the end of the paper roll. This extra step helps to prevent the folded material from “springing” back up away from the end of the paper roll. Depending on the flexibility of the roll wrap material to be crimped and the number of layers in the wrap overhang, folding alone may not be sufficient to ensure an effectively crimped package.
The crimped wrap overhang serves two functions. It provides a surface against which the outside head is placed and sealed to complete a package. Additionally, after the package is complete, the crimped wrap overhang provides a protective buffer inside the package between the end of the paper roll and the floor when the paper roll is stored on its end. It is essential to create a “regular” or successfully crimped wrap overhang. The more regular the crimp, the more effective the crimped material acts as a cushion and protection for the end of the paper roll.
Current practice usually involves the use of crimping wheels which engage the wrap overhang while in rotation. A typical crimper wheel consists of a disc having a number (typically 4 to 6) of crimping paddles or blocks. The disc is usually mounted on the end of a drive shaft which rotates the crimper wheel. The drive shaft is supported by a pivot arm, which holds the drive shaft at one end to lift and lower the crimper wheel relative to the wrap overhang. When the crimper wheel is lowered into a crimping position, the paper roll is also caused to rotate. During this process, wrap overhang is “slapped” by the crimping blocks, pushing the wrap overhang towards the centre of the roll end. As the paper roll is rotated, new wrap overhang is continuously presented to the crimper. This continues until the entire wrap overhang has been crimped.
Crimpers of the above-mentioned type are well known in the prior art, and are typically incorporated into standard paper roll packaging assembly stations. U.S. Pat. No. 5,642,600, issued to Hooper et al., discloses an apparatus for wrapping, crimping and plating a wrapped roll at a single station. The crimper includes a plurality of crimper paddles that slide against the overhanging wrapper to fold it to the roll end when the crimper paddles are rotated as a unit about a horizontal axis. Similar crimpers of this sort in the package wrapping industry are shown in U.S. Pat. No. 6,678,928, issued to Wallace, and U.S. Pat. No. 6,381,921, issued to Tale' et al.
There exist certain problems with these “paddle-type” crimpers. Determining optimal crimping block/paddle geometry has traditionally been arbitrary, left in the hands of skilled professionals who have selected the shapes and number of blocks based on their own personal experience with the crimper. A scientific approach to crimper design is largely unknown and daunting, considering the number of dynamic variables to be considered, including the optimal width of the block, the rotational speed of the crimping wheel, and the thickness of the wrap overhang. Because of the apparent lack of crimper design standards, it has been difficult to efficiently achieve uniform and effective crimping of wrap overhang of different materials and sizes. Many of the crimpers currently in operation are ineffective in producing a stable, effective crimp. These crimpers merely fold the wrap overhang on the ends of the paper roll without creasing the folds that are generated. Consequently, there is an increased risk for damage to the paper rolls resulting from improper packaging.
Current technology has been most successful in producing crimps with 4″ of wrap overhang. For wider wrap overhangs, the quality of the crimping diminishes. While typical crimps produced with 4–6″ of wrap overhang are acceptable, poor results are achieved when the wrap overhang exceeds 6″. With a wide range of paper roll widths to wrap, and the limited choice of wrapper stock widths in most packaging factories to meet the needs of discriminating clientele, it is inevitable that the lengths of certain wrap overhangs will be outside the optimum range for crimping. With poor crimping comes non-uniform crimp pitch, wrinkling and bunching of the roll wrap. Thus, there is a need to prevent undesirable results when crimping wrap overhang longer than about 6″.
There also exist problems when current crimpers are used with heavier wrapping material, such as heavy kraft paper. The problems arise in situations of increased friction between the crimper blocks and the wrap overhang. It has been found that abrupt engagement of current crimpers and the wrap overhang contributes to an irregular crimp pitch, leading to wrinkling and unwanted creasing of the wrap overhang. This is undesirable, as an improperly crimped wrap overhang can allow the contents of the paper roll to be exposed to the elements, such as moisture and dirt. Also, an outer head cannot properly adhere to the end of the paper roll. This can result in damage to the paper roll when the paper roll is positioned on end (as is commonly done in paper roll storage facilities).
To reduce friction, freely-rotatable crease rollers have been used in the wrapping industry as well as many other related industries. Crease rollers of this type appear in several prior art crimper systems. U.S. Pat. No. 3,924,375, issued to Brenner et al., discloses a crimping device for crimping the projecting ends of dual-wrap paper wrapped around the circumference of a roll. The device comprises a displacement member for starting displacement of the projecting wrapper ends, a tucking member which operates after the displacement member to tuck the displaced ends toward the roll end, and a rolling member following the tucking member for rolling the tucks into flat successive crimps against the roll ends. The three members are mounted to a swinging arm which engages the members into a crimping position against the roll. The crimping action takes place along the circumference of the roll end. A problem with this arrangement is evident in, for example, FIG. 6 of Brenner et al. There is an increased risk for wrinkling and improper creasing of the wrap overhang, since the folds must align properly to ensure a smooth crimp.
U.S. Pat. No. 5,907,941, issued to Fukuzumi et al., describes a film roll wrapping apparatus comprising a folding unit for folding a protruding part of a photographic film roll. Folding blades abut against protruding parts and fold them down onto the end face of the photographic film roll. As the roll is rotated, the folded wrap is heat-sealed to the end of the roll by a heating roller, followed by a cooling roller. Both rollers are positioned along the circumference of the roll.
U.S. Pat. No. 4,845,919 discloses an apparatus for folding and pleating “ears” of packaging material wrapped around a cylindrical article. A bending guide is pressed against the side surface of a roll and a folding unit (comprising a pressing device, a folding roll and a folding claw) swings to press the ear of the packaging material. As the folding unit and the roll rotate relative to each other, a folding claw is engaged to fold in the pressed ears.
U.S. Pat. No. 5,174,095 discloses a device for packaging a rolled web comprising a feed roller which rolls in the direction of the rotating rolled web, a rotating folding member (truncated cone rotating opposite to the direction of the web roll), and a fold-keeping plate for holding the folded sections toward the web roll.
In the above-described crimpers, and other known devices having a crimp-roller mechanism, the crease rollers typically serve to crease (or press down to keep folded) wrap overhangs along the circumference of the roll end. This can be potentially disadvantageous, considering the rapid crimping required in high-throughput operations. Bunching of the wrap overhang can occur, particularly at the beginning and end of the crimping action. This results in less-than-optimal crimping and packaging of the paper roll, decreasing efficiency and adding unnecessary expense to the operation.
It is, therefore, desirable to provide a crimper and method of crimping that reduces the occurrence of poor quality crimps and is especially suitable for crimping wrap overhangs of more than 6 inches.